Caption: Histamine molecule. Computer model showing the structure of a molecule of histamine. Atoms are colour-coded (carbon: dark grey, hydrogen: light grey, nitrogen: blue). Histamine is a biogenic amine involved in local immune responses as well as regulating physiological function in the gut. It also acts as a neurotransmitter. Histamine triggers the inflammatory response as part of an immune response to foreign pathogens. It is produced by basophils and by mast cells found in nearby connective tissues.